1. Field of the Invention
The present invention relates generally to a wafer polishing apparatus, and more particularly to a wafer polishing apparatus which is used with a chemical mechanical polishing (CMP) method.
2. Description of Related Art
A wafer polishing apparatus disclosed in Japanese Patent Provisional Publication No. 8-339979 is provided with a holding head (a carrier), a polishing pad (a polishing cloth), and a seal member. A liquid supply passage is formed in the holding heads and a pressurized liquid is supplied into a space enclosed by the holding head, a substrate (a wafer) and the annular seal member through the liquid supply passage, and the substrate is polished while it is pressed against the polishing pad by the pressure of the pressurized liquid.
The liquid supply passage is formed coaxially with the rotary shaft of the holding head, and the pressurized liquid is jetted toward the center of the substrate through the liquid supply passage.
According to the above-described wafer polishing apparatus, the liquid supply passage is formed at such a position as to propel the pressurized liquid toward the center of the substrate. For this reason, the pressure of the pressurized liquid applied to the substrate becomes less as it moves farther, from the center of the substrate. For this reason, the above-described wafer polishing apparatus cannot polish the substrate under a uniform pressure force.